The invention relates to pipe couplings and particularly to a threaded coupling for smooth plastic pipes.
In a known threaded coupling of this general type, on screwing down the sleeve nut against the housing for the purpose of tightening the screwed pipe joint, there is an axial displacement of an inner conical surface via the gripping member. As a result, the member, which in this case, is in the form of a loose, axially slit collet, initially undergoes a constriction, so that the pipe end introduced up to the base of the housing member is secured. Another known construction has a gripping member connected in one part with the housing member and an elastomeric gasket is inserted in a slot of the housing so as to project inwardly.
In these constructions, the elastomeric gasket must be somewhat narrower than the external diameter of the pipe and is expanded by the pipe during the insertion of the latter, thereby bringing about a seal. This has the disadvantage that the gasket is easily damaged by the pipe end which is often sharp-edged, or by grooves of the pipe surface and it can even be displaced from its seat in the housing member.